Traditionally, obtainment of an industrially useful alga has relied on collection and selection of algae. Alternatively, attempts have been made to alter an alga into a more useful one by crossbreeding. However, crossbreeding and selection require a long period for cultivation and a lot of labor, and have not produced sufficient results.
Modification of land plants using genetic engineering techniques has been frequently carried out and produced some successful results. On the other hand, no successful case of modification using genetic engineering techniques or even expression of a transferred gene is known for marine macroalgae.
A promoter suitable for the host to be used is indispensable to in vivo expression of a gene. Accordingly, if one intends to express a gene in an alga, a promoter that operates in the alga is indispensable. However, there has been no known promoter derived from an alga to date. Therefore, it has been impossible to express a gene in an alga.